Channel Sounding Using Multiplicative Arrays Based on Successive Interference Cancellation Principle (2501.11093v1)

Abstract: Ultra-massive multiple-input and multiple-output (MIMO) systems have been seen as the key radio technology for the advancement of wireless communication systems, due to its capability to better utilize the spatial dimension of the propagation channels. Channel sounding is essential for developing accurate and realistic channel models for the massive MIMO systems. However, channel sounding with large-scale antenna systems has faced significant challenges in practice. The real antenna array based (RAA) sounder suffers from high complexity and cost, while virtual antenna array (VAA) solutions are known for its long measurement time. Notably, these issues will become more pronounced as the antenna array configuration gets larger for future radio systems. In this paper, we propose the concept of multiplicative array (MA) for channel sounding applications to achieve large antenna aperture size with reduced number of required antenna elements. The unique characteristics of the MA are exploited for wideband spatial channel sounding purposes, supported by both one-path and multi-path numerical simulations. To address the fake paths and distortion in the angle delay profile issues inherent for MA in multipath channel sounding, a novel channel parameter estimation algorithm for MA based on successive interference cancellation (SIC) principle is proposed. Both numerical simulations and experimental validation results are provided to demonstrate the effectiveness and robustness of the proposed SIC algorithm for the MA. This research contributes significantly to the channel sounding and characterization of massive MIMO systems for future applications.

• The paper introduces a novel channel sounding method employing multiplicative arrays (MA) for efficient parameter estimation in ultra-massive MIMO systems.
• It applies a successive interference cancellation (SIC)-based algorithm to mitigate fake paths and accurately estimate channel characteristics like delay and angles.
• Experimental and simulation results demonstrate a 49.3% reduction in antenna elements while maintaining high channel sounding performance.

Channel Sounding with Multiplicative Arrays and SIC

The paper "Channel Sounding Using Multiplicative Arrays Based on Successive Interference Cancellation Principle" explores an advanced methodology for radio channel sounding, specifically within ultra-massive MIMO systems, utilizing multiplicative arrays (MAs). The authors aim to address issues of high complexity, cost, and measurement time associated with conventional real and virtual antenna array-based sounders.

Figure 1: (a) Architecture of the URA. (b) Distribution of array element in the URA. (c) Architecture of the MA. (d) Distribution of array element in the MA.

Introduction

Advancements in wireless communication technologies necessitate enhanced approaches to channel sounding, particularly for the development of massive MIMO systems in the context of emerging 6G networks (2501.11093). With projections suggesting that future 6G systems will support arrays potentially numbering over a thousand antennas, efficient channel sounding becomes increasingly challenging due to the associated complexities and costs of large-scale antenna systems.

In response to the limitations of existing channel sounding solutions, this paper introduces the concept of multiplicative arrays for channel sounding applications. By leveraging the orthogonal array structure of MAs, the authors propose a novel approach to achieving significant reductions in the number of required antenna elements while maintaining effective system performance for channel characterization. The integration of the successive interference cancellation (SIC) principle enables the mitigation of fake paths and distortion issues in multipath scenarios.

Multiplicative Array Design for Channel Sounding

The core innovation in the described research is the introduction of the multiplicative array (MA) structure in the channel sounding domain. MAs employ two orthogonally arranged linear sub-arrays to mimic the array factor of a uniform rectangular array (URA) with fewer antenna elements (Figure 1). This design has been successful in radio astronomy and offers high angular resolution and cost efficiency in channel sounding.

A detailed mathematical derivation is employed to characterize the performance of the MA, revealing its synthesis and spatial channel sounding capabilities.

Successive Interference Cancellation (SIC) for Parameter Estimation

One significant challenge in employing MAs for channel sounding is the introduction of fake paths due to the array's multiplicative nature (Figure 2). The paper addresses this challenge by proposing a successive interference cancellation (SIC)-based multi-path estimation algorithm tailored specifically to harness these unique characteristics of MAs.

The algorithm's foundation lies in iteratively removing the channel frequency response (CFR) of the strongest detected path, which subsequently eliminates fake path interference (Algorithm 1). It effectively estimates the necessary channel parameters such as elevation and azimuth angles, delay, and power. The results from extensive numerical simulations and experimental validations support the algorithm's robustness and ability to preserve accuracy.

Numerical Simulations and Experimental Validation

The authors conducted both numerical simulations and experimental validations to evaluate the effectiveness of the proposed methods.

In the numerical studies, they examined multi-path scenarios with wideband signal propagation from 26 to 30 GHz across 1500 frequency points. The proposed approach effectively identified and discriminated true multipath components from fake paths in both delay and angular domains, as demonstrated in (Figures 4 and 5).

In the experimental validation (Figure 3), the setup involved a meeting room environment with a virtual antenna array system (VAA), using a vector network analyzer and biconical antennas at a center frequency of 27 GHz (2501.11093). Measurements validated the accuracy of the proposed SIC algorithm for channel parameter estimation, aligning closely with standard URA-based methods while providing a remarkable reduction in the number of required antennas by approximately 49.3% without significant degradation in parameter estimation accuracy (Table 2).

Figure 2: An illustration of the occurrence of fake paths with two incident paths.

Figure 4: (a) The power pattern of the URA with two paths in $(u,v)$ space. (b) The power pattern of the MA with two paths in $(u,v)$ space.

Figure 5: (a) The PADP of the URA with two paths. (b) The PADP of the MA without using the proposed algorithm. (c) The PADP of the MA with the proposed algorithm.

Figure 6: The detailed PADP of the MA with corresponding CIR processed by proposed algorithm in first three iterations.

Figure 3: Measurement scenario viewed from the Tx antenna.

The outcome was a demonstration of substantial resource saving. The researchers used the MA, comprising a total of 38 elements, effectively reducing the number of antennas required, compared to the 75 elements in the URA configuration, achieving a 49.3% reduction in elements without significant loss in channel sounding performance (Table 2).

Conclusion

This paper presents a significant contribution to massive MIMO channel sounding technology using the multiplicative array (MA) structure, enabled by the application of successive interference cancellation (SIC) techniques. The derived mathematical expressions and empirical studies validate the capability of MAs to perform efficient wideband spatial channel sounding, significantly reducing the number of antenna elements while maintaining robustness in parameter estimation. The implications of this research are significant for the future design and implementation of channel sounders, particularly those employed in ultra-massive MIMO systems for 5G and beyond-5G wireless communication networks. Future work could potentially explore further enhancements of the SIC algorithm for even more complex multi-path scenarios and dynamic environments, as anticipated in emerging 6G technologies.